Design And Calibration Of Micro-Piezoresistive Pressure Sensor With High Performance

The principle of MEMS piezoresistive pressure sensor is mainly based on the piezoresistive effect of semiconductor.This kind of sensor is characterized with the merits of small size,high linearity,high sensitivity,high integration,low cost and simple manufacturing,etc..It is widely used in precision instruments and other related fields.However,due to the properties of semiconductor materials and the random errors in the processing process,the piezoresistive pressure sensor has problems such as zero failure,poor linearity,and serious temperature drift.In recent years,the requirements for the measurement accuracy of the pressure sensor in the high-end field have become increasing.It is of great significance and application value to study the temperature calibration of pressure sensor to reduce the impact of temperature on the sensor and improve the accuracy and reliability of the sensor.In this thesis,a high-performance SOI-based nano-silicon film micro-piezoresistive pressure sensor is designed and implemented firstly,with its measurement error analyzed.The necessity of the design of pressure sensor calibration system is pointed out.Because the pressure sensor temperature calibration system needs to obtain accurate temperature information of the pressure sensor,a BJT-based CMOS temperature sensor with calibration function is designed,with the proposed corresponding wafer level three-step calibration technology.Finally,aiming at the measurement errors of the piezoresistive pressure sensor,a temperature calibration architecture for pressure sensors is designed,including the designed CMOS temperature sensor,and a new calibration algorithm is proposed.The main contents of this thesis include the following parts:(1)Aiming at the problems of low linearity,low sensitivity and poor temperature characteristics of traditional piezoresistive pressure sensors,a high-performance SOI-based nano-silicon film micro-piezoresistive pressure sensor is designed and realized by optimizing the structure of the sensitive film and the material,size and layout of the piezoresistor at the design stage of the sensor.The measured results demonstrate that the designed sensor shows a high sensitivity of 0.45 m V/(k Pa·V)and the nonlinearity of 0.108 %F.S with the pressure range of 0～40 k Pa at room temperature.In the working temperature range of-40 ℃～125 ℃,the zero temperature drift coefficient and sensitivity temperature drift coefficient of the sensor are0.0047 %F.S and 0.089 %F.S,respectively,showing good temperature stability.(2)In view of the low accuracy of the external temperature sensor in the pressure sensor temperature calibration system,a BJT-based CMOS temperature sensor with calibration function is designed.The sensor is calibrated at the wafer level based on the proposed threestep calibration technology.The experimental results show that the calibrated sensor can realize an inaccuracy(±3δ)within ±0.3 °C from-40 °C to 125 °C.This calibration technology can effectively eliminate the error band of sensor output caused by process error in batch manufacturing.(3)Aiming at the problems of piezoresistive pressure sensor,such as zero failure,nonlinearity,zero temperature drift,sensitivity temperature drift,etc.,the temperature calibration architecture of the pressure sensor is designed firstly,and the calibration process of the system is introduced.Secondly,a new calibration algorithm of pressure sensor is proposed.The algorithm obtains nine calibration coefficients by testing three temperature points and four pressure points.Substitute the nine calibration coefficients into the calibration formula,and the corresponding calibrated output voltage can be calculated for any pre-calibrated output voltage within the applicable pressure and temperature range.